/Engine/Plugins/Importers/USDImporter/Source/USDStage/Public/USDStageActor.h
If IsolatedStageRootLayer is the identifier of one of the sublayers of the currently opened stage, this will enter isolated mode by creating a new stage with IsolatedStageRootLayer as its root, and displaying that. Provide an empty string to leave isolated mode.
[UFUNCTION](Programming/UnrealArchitecture/Reference/Functions)(BlueprintCallable, Category="USD", Meta=(CallInEditor="true")) void SetIsolatedRootLayer ( const [FString](API\Runtime\Core\Containers\FString) & IsolatedStageRootLayer )